External heat exchange pad for patient

ABSTRACT

An intravenous heat exchange catheter and/or an external cooling pad/bladder can be used to maintain hypothermia in, e.g., a cardiac arrest patient, but to accelerate the cooling process the patient first can be infused with cold saline before the opportunity arises to connect the catheter or pad to the patient.

This is a divisional of Ser. No. 11/108,281, filed Apr. 18, 2005 nowU.S. Pat. No. 7,070,612 from which priority is claimed.

FIELD OF THE INVENTION

The present invention relates generally to therapeutic hypothermia.

BACKGROUND OF THE INVENTION

Intravascular catheters have been introduced for controlling patienttemperature. Typically, a coolant such as saline is circulated throughan intravascular heat exchange catheter, which is positioned in thepatient's bloodstream, to cool or heat the blood as appropriate for thepatient's condition. The coolant is warmed or cooled by acomputer-controlled heat exchanger that is external to the patient andthat is in fluid communication with the catheter.

For example, intravascular heat exchange catheters can be used to combatpotentially harmful fever in patients suffering from neurological andcardiac conditions such as stroke, subarachnoid hemorrhage,intracerebral hemorrhage, cardiac arrest, and acute myocardialinfarction, or to induce therapeutic hypothermia in such patients.Further, such catheters can be used to rewarm patients after, e.g.,cardiac surgery or for other reasons. Intravascular catheters affordadvantages over external methods of cooling and warming, including moreprecise temperature control and more convenience on the part of medicalpersonnel.

The following U.S. patents, all of which are incorporated herein byreference, disclose various intravascular catheters/systems/methods:U.S. Pat. Nos. 6,419,643, 6,416,533, 6,409,747, 6,405,080, 6,393,320,6,368,304, 6,338,727, 6,299,599, 6,290,717, 6,287,326, 6,165,207,6,149,670, 6,146,411, 6,126,684, 6,306,161, 6,264,679, 6,231,594,6,149,676, 6,149,673, 6,110,168, 5,989,238, 5,879,329, 5,837,003,6,383,210, 6,379,378, 6,364,899, 6,325,818, 6,312,452, 6,261,312,6,254,626, 6,251,130, 6,251,129, 6,245,095, 6,238,428, 6,235,048,6,231,595, 6,224,624, 6,149,677, 6,096,068, 6,042,559.

Surface cooling may be less optimally used. For example, externallyapplied cooling pads are disclosed in U.S. Pat. Nos. 6,827,728,6,818,012, 6,802,855, 6,799,063, 6,764,391, 6,692,518, 6,669,715,6,660,027, 6,648,905, 6,645,232, 6,620,187, 6,461,379, 6,375,674,6,197,045, and 6,188,930 (collectively, “the external pad patents”), allof which are incorporated herein by reference.

Regardless of the modality of cooling, it is believed that the sooner apatient is cooled after ischemic insult, the better the therapy. Thepresent invention recognizes that many patients will have their firstencounter with health care personnel in ambulances, prior to beingafforded the opportunity for critical care such as controlledmaintenance of hypothermia. Thus, it would be advantageous, asunderstood herein, to provide a means to bring cooling on board topatients as soon as possible.

SUMMARY OF THE INVENTION

A system for controlling patient temperature includes a closed loop heatexchange catheter configured for placement in the circulatory system ofa patient to exchange heat with the blood of the patient. The systemalso includes a source of cold fluid, with the cold fluid being colderthan normal body temperature and infusable from the source into thepatient without using the catheter.

The catheter may be configured for percutaneous advancement into thecentral venous system of the patient. The catheter can carry coolantthat is not infused into the bloodstream of the patient.

In another aspect, a method for treating a patient using hypothermiaincludes injecting cold saline into the venous system of the patientwhile the patient is located in an ambulance or in an emergency room ofa hospital. Then subsequently hypothermia is maintained in the patientusing an external heat exchange pad or an intravascular heat exchangecatheter while the patient is in an operating room of a hospital or anintensive care unit of a hospital.

In yet another aspect, a method for treating a patient includes infusinginto the patient's venous system a cold fluid having a temperature lowerthan a temperature of the patient to cause the fluid to mix with theblood of the patient and thereby to cool the patient. The method alsoincludes engaging a cooling apparatus with the patient to maintain adesired hypothermic condition in the patient.

In additional embodiments, a system for controlling patient temperatureincludes a closed loop heat exchange catheter configured for placementin the circulatory system of a patient to exchange heat with the bloodof the patient, and an external heat exchange bladder configured forexchanging heat with the skin of a patient. The system also includes aheat exchange system in a single housing and engageable with both thecatheter and the bladder.

In non-limiting implementations of this last embodiment, the housing caninclude a sensor which detects when the heat exchange system isconnected to the bladder, and potentially to the catheter as well, toprovide a signal to a controller in the housing. Additionally, acontroller may be in the housing and receive a patient temperaturesignal from a BTT sensor. Further, an IV bag can be supported on thehousing for infusing cold saline directly into the bloodstream of apatient.

Continuing to summarize non-limiting implementations, the heat exchangesystem may include a coolant loop configured for exchanging heat with aworking fluid loop associated with the catheter. The coolant loop mayalso be configured for direct fluid communication with the bladder. Or,the heat exchange system can include a coolant loop having a coldwell,with the catheter being associated with a catheter working fluid loopincluding a catheter coil disposable in the coldwell and with thebladder being associated with a bladder working fluid loop including abladder coil disposable in the coldwell. Both working fluid loops may beassociated with respective pumps. The heat exchange system may alsoinclude an internal reservoir for priming the bladder, and may controlboth the catheter and bladder simultaneously. The heat exchange systemcan include a refrigerant loop including a compressor and one or moreheat exchangers communicating with the compressor.

In another aspect, a heat exchange system includes a coolant loop, atleast a first working fluid loop in thermal communication with thecoolant loop and an intravascular heat exchange catheter associated withthe first working fluid loop such that working fluid circulates throughthe heat exchange catheter without entering the patient's bloodstreamwhen the catheter is positioned in the bloodstream. At least oneexternal heat exchange member is configured for placement against apatient's skin to heat or cool the skin. The external heat exchangemember is configured for heat transfer using the coolant loop.

In another aspect, a method for patient temperature control includesproviding a heat exchange system, and engaging an intravascular heatexchange catheter with the system and with a patient to exchange heatwith the patient. The method also includes engaging at least one bladderwith the system and placing the bladder against the patient's skin toexchange heat with the patient.

In other aspects, a patient temperature control system includes at leastone bladder through which working fluid can flow. The bladder ispositionable against the skin of a patient, and a skin conditioninghydrogel can be disposed between the bladder and the skin.

In another aspect, a patient temperature control system includes atleast one bladder through which working fluid can flow, with the bladderbeing configured as the front of a garment and having a trunk portionand two opposed limb portions that can drape over the patient.

In another aspect, a patient temperature control system includes atleast one bladder through which working fluid can flow. The surface ofthe bladder facing away from a patient when the bladder is positionedagainst the skin of the patient is backed by a foam that conforms topressure caused by the weight of the patient.

The details of the present invention, both as to its structure andoperation, can best be understood in reference to the accompanyingdrawings, in which like reference numerals refer to like parts, and inwhich:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing two modalities of controlledhypothermnia maintenance in a patient, along with an apparatus forquickly reducing patient temperature;

FIG. 2 is a flow chart of logic;

FIG. 3 is a diagram of a single heat exchange chassis system thatsupports both an external cooling bladder and an intravasculartemperature control catheter;

FIG. 4 is a schematic diagram showing that the heat exchange system canhave two heat exchangers in parallel with one compressor;

FIG. 5 is a schematic diagram of an alternate system;

FIG. 6 is a cross-section of a non-limiting quick disconnect feature aswould be seen along the line 6-6 in FIG. 5;

FIG. 7 is a schematic diagram of an alternate system; and

FIG. 8 is a schematic diagram of an alternate system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring initially to FIG. 1, a system is shown, generally designated10, that includes a heat exchange catheter 12 that is in fluidcommunication with a catheter temperature control system 14.

In accordance with present principles, the system 10 can be used toinduce therapeutic hypothermia in a patient 16 using a catheter in whichcoolant circulates in a closed loop, such that no coolant enters thebody. While certain preferred catheters are disclosed below, it is to beunderstood that other catheters can be used in accordance with presentprinciples, including, without limitation, any of the cathetersdisclosed in the following U.S. patents, all incorporated herein byreference: U.S. Pat. Nos. 5,486,208, 5,837,003, 6,110,168, 6,149,673,6,149,676, 6,231,594, 6,264,679, 6,306,161, 6,235,048, 6,238,428,6,245,095, 6,251,129, 6,251,130, 6,254,626, 6,261,312, 6,312,452,6,325,818, 6,409,747, 6,368,304, 6,338,727, 6,299,599, 6,287,326,6,126,684. The catheter 12 may be placed in the venous system, e.g., inthe superior or inferior vena cava.

Instead of or in addition to the catheter 12, the system 10 may includeone or more pads 18 that are positioned against the external skin of thepatient 16 (only one pad 18 shown for clarity). The pad 18 may be,without limitation, any one of the pads disclosed in the external padpatents. The temperature of the pad 18 can be controlled by a padcontroller 20 in accordance with principles set forth in the externalpad patents to exchange heat with the patient 16, including to inducetherapeutic mild or moderate hypothermia in the patient in response tothe patient presenting with, e.g., cardiac arrest, myocardialinfarction, stroke, high intracranial pressure, traumatic brain injury,or other malady the effects of which can be ameliorated by hypothermia.

To cool the patient while awaiting engagement of the catheter 12 and/orpad 18 with the patient, cold fluid 22 in a cold fluid source 24 may beinjected into the patient and in particular into the patient's venoussystem through a pathway 26. Without limitation, the pathway 26 may anIV line, the source 24 may be an IV bag, and the fluid 22 may be chilledsaline, e.g., saline at the freezing point or slightly warmer. Or, thesource may be a syringe, and the saline can be injected directly intothe bloodstream of the patient.

Now referring to FIG. 2, at block 28 the patient presents with symptomsindicating that the application of hypothermia is appropriate. Forinstance, the patient may have cardiac arrest, and may be resuscitated.Or, the patient may present with myocardial infarction or stroke orother malady.

At block 30, cold saline 22 is immediately (in the case of cardiacarrest patients, immediately after resuscitation) injected into thepatient's bloodstream, preferably at a venous site, using the source 24.This can occur in, e.g., an ambulance on the way to the hospital forfurther temperature management, and/or in the hospital emergency room.Hypothermia treatment including the establishment and maintenance ofmild or moderate hypothermia subsequently is effected at block 32 usingthe catheter 12 and/or pad 18, typically in the operating room orintensive care unit of a hospital, although in some hospitals the stepat block 32 may begin while the patient is still in the emergency roomor even while the patient is still in the ambulance.

The above three modalities of cooling—intravascular closed loopcatheter, external pad/bladder, and cold saline bolus infusion—may besupported by a single housing.

With greater specificity, FIG. 3 shows details of one non-limitingsingle-chassis heat exchange system, generally designated 100, whichincludes a single heat exchange system housing 102 holding all orportions of three fluid loops. Specifically, a refrigerant loop 104exists in which refrigerant flows between a compressor 106 and at leastone heat exchanger 108. Exiting the heat exchanger 108, the refrigerantpasses through a CP valve 110 to a condenser 112, which condenses therefrigerant. The refrigerant loop 104 may be replaced by athermoelectric cooling loop in which the fluid is air passing over andcooling a TEC element.

In the heat exchanger 108, the refrigerant expands to cool a coolant ina coolant loop 114, which is in thermal but not fluid contact with therefrigerant loop 104. The coolant may be water, propylene glycol, amixture thereof, or other suitable coolant. Also included in the coolantloop 114 is a heater 116 for heating the coolant to, e.g., re-warm apatient, and a coolant pump 118 to circulate the coolant through thecoolant loop 114. The coolant pump may be a magnetically-couplednon-displacement pump, or a positive displacement pump.

FIG. 3 shows that the coolant flows into a chamber defined by a coldwell120, which may be the highest point in the system. A catheter fluid loopcoil 122 may be disposed in the coldwell 120 in thermal but not in fluidcontact with the coolant. The catheter fluid loop coil 122 defines partof a working fluid loop 124 through which a working fluid such as salineflows. The fluid in the working fluid loop 124 circulates, under theinfluence of a working fluid pump 126, which can be a peristaltic pump,through an intravascular heat exchange catheter 128 without exiting thecatheter into the bloodstream. The working fluid exchanges heat with thecoolant in the coldwell 120. A saline bag 130 may be provided in theworking fluid loop 124 for priming purposes, and an air trap 132 mayalso be provided to prevent any air that might exist in the workingfluid loop 124 from entering the catheter 128. The entire working fluidloop 124 may be provided as a standalone catheter start-up kit, with thecatheter fluid loop coil 122 disposed by medical personnel in thecoldwell 120 and with the catheter 128 then being advanced into thevasculature of a patient to exchange heat with the patient. Additionaldetails of the non-limiting system 100 may be found in the presentassignee's U.S. Pat. Nos. 6,146,411, 6,581,403, and 6,529,775, all ofwhich are incorporated herein by reference, and in U.S. patentapplication Ser. No. 10/944,544, filed Sep. 17, 2004, also incorporatedherein. The above patents further disclose non-limiting ways in which acontroller/power supply 133 controls various of the components above toheat or cool the working fluid as necessary to achieve a user-set targettemperature. A patient temperature sensor 133 a can send a patienttemperature signal to the controller 133 as shown. The sensor 133 a maybe any suitable sensor including, without limitation, a braintemperature tunnel (BTT) sensor to sense the temperature through thinperi-occular skin of a sinus, which represents the temperature of thebrain.

Still referring to FIG. 3, in lieu of placing the catheter fluid loopcoil 122 in the coldwell 120 and the catheter 128 in the patient, abladder cooling loop coil 134, which is part of a bladder fluid loop136, may be disposed in the coldwell 120. A bladder fluid pump 138,which can be a positive displacement pump, circulates working fluid,which could be tap water or saline or other appropriate fluid, throughthe loop 136. Included in the loop 136 is an externally-applied bladder140 through which the working fluid flows to cool a patient. The bladder140 may be any suitable cooling device such as a conformal pad or amattress that is placed against the skin, including any of the devicesreferred to previously. An adhesive or non-adhesive hydrogel and/or asilver sulphur diazene cream or zinc paste may be disposed between thebladder and patient. Or, a skin conditioning hydrogel such as glycerolin sorbolene can be used. The bladder itself may be configured, as shownat 1000 in FIG. 1, as the front of a shirt or trousers, i.e., with atrunk portion and two opposed limb portions that can drape over thepatient. The surface of the bladder that faces away from the patient canbe backed by a NASA foam that conforms to pressure caused by the weightof the patient to reduce the risk of bedsores.

A saline bag 142 may be provided in the loop 136 for priming. Also, athree-way stopcock 144 can be provided as shown to isolate the bag 142.The loop 136 may be controlled by a separate bladder controller/powersupply 146, which may communicate with the controller 133 if desired.

An IV pole 147 may be mounted on the housing 102 and may support an IVbag 148, for infusing cold saline in the IV bag directly into thebloodstream of the patient as shown. A coil 149 may be provided incommunication with the IV bag. The coil 149 may be disposed in thecoldwell 120 to cool saline in coil, which can circulate under theinfluence of a pump 149 a.

FIG. 4 shows that for greater heat exchange power, a compressor 150 maycirculate refrigerant through two heat exchangers 152, 154, either inparallel with each other or with one of the heat exchangers isolated bymeans of a computer-controlled solenoid valve 156. The arrangement shownin FIG. 4 could be used in lieu of the arrangements shown in the otherfigures herein.

FIG. 5 shows the coolant loop portion 200 of an alternate system 202,which in all essential respects is identical to the system 100 shown inFIG. 3 with the following exceptions. Coolant such as water may flow,under the influence of a coolant pump 204, through a heat exchanger 206and a computer-controlled three-way valve 208, which either sends thecoolant to a coldwell 210 to exchange heat with the coil of anintravascular catheter as described above, or to a bladder loop 212 thatincludes an external heat exchange bladder 214 as shown. A primingreservoir 216, which can be internal to the chassis of the system 202,may be provided for priming the bladder 214 with coolant, it beingunderstood that in some embodiments the coldwell itself can be used forpriming instead, in which case an additional three-way valve between thecoldwell and first three-way valve 208 could be required forestablishing the appropriate fluid flow control.

In any case, as shown in FIG. 5 the bladder 214 is connected to a supplyline 218 and a return line 220, with the lines 218, 220 terminating inrespective bladder fittings 222, 224 that engage respective systemfittings 226, 228 on the chassis of the system 202. Preferably, thefittings are quick disconnect fittings that provide an indication ofengagement and disengagement to the controller (not shown) of the system202 for establishing the position of the three-way valve 208 forcatheter or bladder operation as appropriate. Thus, in FIG. 5 thecoolant loop supplies either the coldwell for exchanging heat with theworking fluid circuit of the intravascular catheter, or it supplies thebladder directly.

It is undesirable that the heat exchanger freeze during, e.g., priming.Accordingly, when the system detects the bladder being connected, it canmaintain system fluid temperatures above the freezing point. In anycase, to avoid skin damage it is preferred that when the bladder is usedthe coolant temperature be maintained between four and forty two degreesCelsius.

A non-limiting example of quick disconnect fittings (using 224, 228 asexamples) is shown in FIG. 6. As shown, the bladder fitting 224 may becircumscribed by a collar 230, and as the bladder fitting 224 isadvanced into the system fitting 228, the collar 230 deflects a ball 232that is reciprocally disposed in the wall of the system fitting 228 andthat is urged inwardly (toward the bladder fitting 224) as shown by aspring 234. As the ball 232 deflects, it actuates a sensing element 236on the system fitting 228 to provide an “engaged” signal to the systemcontroller, which can then reconfigure the user interface and/or controlparameters used for establishing patient temperature. Or, the ball andspring can be omitted and the collar seat against the sensing elementwhen the fittings are engaged, to actuate the sensing element. Otherarrangements known in the art may be used. The sensing element 236 maybe an electrical contact or other suitable element known in the art. Itis to be understood that the catheter start-up kit shown in FIG. 3 mayalso be connected to the system using such fittings, so that in any ofthe embodiments herein, the controller “knows” which device or devices,catheter and/or bladder, is connected.

FIGS. 7 and 8 show alternate embodiments in which a bladder 300 is partof a bladder working fluid loop 302 that includes a bladder coil 304disposable in a bladder coldwell 306, it being understood that thecatheter-related working fluid loop shown in FIG. 3 with separatecatheter coldwell and catheter working fluid loop pump is also providedin a system that includes the refrigerant loop and working fluid loopshown in FIG. 3. In essence, in the systems of FIGS. 7 and 8 twoseparate working fluid loops are provided, one for the external coolingbladder and one for the intravascular catheter, with both loops beingcontrolled by a common controller, e.g., the controller 303 shown inFIG. 3. In any case, a bladder working fluid loop pump 308 provides themotive force for circulating the working fluid. Either an externalsaline bag 310 (FIG. 7) can be provided for priming through a three-waystopcock 312, or a reservoir 314 (FIG. 8) that is internal to the systemchassis can be provided. In both cases, a supply line 316 to the coil304 and a return line 318 from the bladder 300 (or from the stopcock 312when one is used as shown in FIG. 7) terminate in quick-disconnectfittings 320, 322 as shown, for operation as described above to alertthe system controller to whether the bladder is connected. In theembodiments shown in FIGS. 7 and 8, since two separate working fluidloops are provided, both the catheter and the bladder canbe.simultaneously controlled by the controller to heat or cool apatient. Or, if simultaneous catheter/bladder use is not required, thebladder loop may not include its own coldwell and pump but rather canuse a single coldwell that services either catheter and bladder.

While the particular SYSTEM AND METHOD FOR BRINGING HYPOTHERMIA RAPIDLYONBOARD as herein shown and described in detail is fully capable ofattaining the above-described objects of the invention, it is to beunderstood that it is the presently preferred embodiment of the presentinvention and is thus representative of the subject matter which isbroadly contemplated by the present invention, that the scope of thepresent invention fully encompasses other embodiments which may becomeobvious to those skilled in the art, and that the scope of the presentinvention is accordingly to be limited by nothing other than theappended claims, in which reference to an element in the singular is notintended to mean “one and only one” unless explicitly so stated, butrather “one or more”. All structural and functional equivalents to theelements of the above-described preferred embodiment that are known orlater come to be known to those of ordinary skill in the art areexpressly incorporated herein by reference and are intended to beencompassed by the present claims. Moreover, it is not necessary for adevice or method to address each and every problem sought to be solvedby the present invention, for it to be encompassed by the presentclaims. Furthermore, no element, component, or method step in thepresent disclosure is intended to be dedicated to the public regardlessof whether the element, component, or method step is explicitly recitedin the claims. No claim element herein is to be construed under theprovisions of 35 U.S.C. §112, sixth paragraph, unless the element isexpressly recited using the phrase “means for” or, in the case of amethod claim, the element is recited as a “step” instead of an “act”.

1. A patient temperature control system including at least one bladderthrough which working fluid can flow, a silver sulphur diazene creambeing disposed on a surface of the bladder facing the skin when thebladder is positioned against a patient, the bladder being configured asthe front of a garment and having a trunk portion and two opposed limbportions that can drape over the patient.
 2. A patient temperaturecontrol system including at least one bladder through which workingfluid can flow, a zinc paste being disposed on a surface of the bladderfacing the skin when the bladder is positioned against a patient.